Automatic telephone system



Feb. 24, 1959 F. sPlEcKER AUTOMATIC TELEPHONE SYSTEM Filed Feb. 20, 1955 l 8 Sheets-Sheet l Feb. 24,' 1959 F. SPIECKER AUTOMATIC TELEPHONE SYSTEM 8 sheetssheet '2 Filed Feb. 20, 1953 mk ck h MW .MU nu Inventar? F. 'PlEcKER AUTOMATIC TELEPHONE SYSTEM Feb, 24, 1959 Filed Feb. 20, 1953 8 Sheets-Sheet 3 8' Sheets-Sheet 4 e SSG LINmQBQvM, .WF1 YQUN m/M @MQ a QN mm wx N kN wvx HH n w \\l a HHH A v. .Wl QF s mmm F ---I E Tm n w w w m. n x En .nn 255km. N A NSN. QN I. hu hw m nu W ,--SN Em F. 'sPlEcKl-:R

AUTOMATIC TELEPHONESYSTEM Feb. 24, 1959 Filed Feb. 20, 1953 '8 Sheets-Sheet 5 Filed Feb. 20, 1953 Feb. 24, 1959 1F.- SPIEQKERA AUTOMATICTELEPHONESYSTEM 8 Sheets-Sheet G Filed Feb. 120, 1953 IW, 65h. gub

Feb. 24, 1959 F. SPIECKER Q AUTOMATIC TELEPHONE SYSTEM Filed Feb. 2o, i955 8 Sheets-Sheet 7 Feb. 24, 1959 F. SPIECKER 2,875,280

AUTOMATIC TELEPHONE SYSTEM, Filed Feb. 2o. 1953 I 8 sheets-sheet a United States Patent O AUTOMATIC TELEPHONE SYSTEM Friedrich Spiecker, Berlin-Charlottenburg, Germany, assignor` to Siemens & Halske Aktiengesellschaft, Munich, Germany, a corporation of Germany Application February 20, 1953, Serial No. 338,103 In Germany February 7, 1950 Public Law 619, August 23, 1954 Patent expires February 7, 1970 18 Claims. (Cl. 179-18) This invention relates to signalling systems and is par l ticularly concerned with an automatic telephone system of the relay type. i

The object ofthe invention is to provide a system of number of the wanted line connected withsuch line byl means of coupling relays.

In a known system there are many small groups of lines combined to form a principal line group. The traftic to all lines of the principal group is taken care of over a large number of intermediate lines. Each ofthe small groups of; lines can however be reached only over a small number of the intermediate lines associated with the j.. large principal group. It is thus impossible to utilize for calls to every subscribers line each intermediate line serving the traic to the corresponding large principal -line group; and it follows, therefore, that the available connecting devices and theintermediate lines cannot be 'fully utilized and their number must consequently be appreciably greater than is warranted by the traffic conditions.v

The invention permits full utilization of the available connecting devices and intermediate lines by subdividing a large main group of subscribers lines into groups, each of said groups containing a plurality of subgroups, and by providing switching means comprising a plurality of switching devices allocated to said main group, a register, a marker, a plurality of serially related couplers, intermediate lines extending between each two of said cou-l plers, a group coupler allocated to each group of lines, a calling subscriber connected to one of said switching devices for extending a call to a wantedlineover said register and said marker, the talking path between the corresponding switching device and `the wanted subscribers line being built up over said serially related couplers and said intermediate lines,` and the group coupler allocated to the group containing the wanted line, whereprevailing by said switching device to which the calling subscriber, is connected may be connected with the wanted line over selection stage of the group TnGrl belonging to the principal group shown in Fig, l;

Fig. 3 part 1 and part 2 represent a relay set ER4, a register ZE and a marker EF; i

` VK to a group of first intermediate lines 1.ZLe.

ICC

Fig. 3a shows a modified circuit for part of the relays of the marker EF shown in Fig. 3 part 2; p Fig. 4 indicates the precoupler VKI, the allotter 1.EO1 and the group coupler GK1;

Fig. 5 illustrates the allotter 2 EO1, the intermediate coupler ZKl, the allotter L01 and the circuit of a subscribers line;

Fig. 6 indicates the manner in which the Figs. 3, 4 and 5 are to be arranged; and

Fig. 7 shows a P. B. X group, theP. B. X lines being distributed in several line groups and subgroups of lines, respectively.

Description of F ig. I

The subscribers lines appear in principal or main groups each having 1000 lines. One such main group is shown and designated by reference TnHGr. If an exchange has a capacity of 1000 lines, such lines form a main group. In larger exchanges, there are several such main groups. A calling subscriber is connected over a group selection stage with a relay set of the main group containing the desired subscribers line. necting devices and intermediate lines ofthe corresponding main group form in such a case the nal selection stage. i i

Each main group is subdivided into four line groups TnGrl TnGr4 each having 250 subscribers lines.

Each line group comprises iive subgroups each having I 50 lines. The subgroups TnUGrl-S thus form theline group TnGrl; the subgroups TnUGr.6-10 form the line group TnGrZ, etc.

The linegroups and the` subgroups may include a greater or a` smaller number of subscribers lines depend.- ing on the traflic requirements.

There are provided 50 connecting devices (relay sets) ERL-10, ERM-20 ER41-50 which serve the calls to the subscribers of a main group. Upon seizure of a relay set by a calling subscriber there is connected a register (not shown in Fig. 1) which contains the digit relays controlled by the dial pulses. Upon completion of the number selection, the wanted subscribers line is marked over a marker (not shown in Fig. l) which is individual to the main group. lf the selected line is idle, a talking path will be completed wihch connects the selected line with the relay set seized by the calling line.

The 50 relay sets ERI-S0 are subdivided into tive groups. Each group has access over its own pre-coupler The number of first intermediate is `equal to the number of relay sets ER. The relay sets ERI-10 form a group. They have access to a group 1.ZLeI of 10 first intermediate lines over the pre-coupler VKI. p

For each of the line groups TnGrl-TnGr4 there is provided a group coupler as indicated at GK1-GK4. Associated with each line group TnGrl TnGr4 are also `second intermediate lines 2.ZLe which may be coupled by coupling relays in the corresponding group coupler GK with the intermediate lines 1.ZLe. The group inter mediate lines 2.ZLe, although being individual to their associated groups, are nevertheless accessible to all relay sets ER over the pre-couplers VKl-VKS and over the group coupler that may be in any instance concerned, that is, they are accessible to the relay set ERI-10 over the pre-coupler VKI and the 10 intermediate lines of the group 1.ZLeI.

All intermediate lines 1.ZLe extend in parallel to the group couplers GK of all line groups. In the path extended from each group coupler there is provided an allotter EO.A In the path extended from the group coupler GK1 there is the allotter 2.1301; and in the path extended from the group coupler GKZ there is the allotter The con- For each of the ve subgroups TnUGr of a line group TnGr there are avaliable 10 subscribers intermediate lines ZLt. g Each such lintermediate line ZLt is branched off in the allotter LO of its subgroup. One of the branches ZLv serves the-outgoing traiiic which does not concern the invention, while the incoming traiiic is taken care of by the other branch is the intermediate line 3.ZLe of the iirst selectionl stage. Over an intermediate coupler, for example ZKI of the subgroup TnUG-rl will be connected an intermediate line 3 ZLe, which is made available vby the allotter L01, to an intermediate group line 2.ZLe which has access over 'the group coupler `GlECl. to the relay set ER that had been seized by the calling subscriber. The making available and seizure of the intermediate lines 1.ZLe, 2.ZLe and 3.ZLe, for example, in a connection to a subscriber `in the subgroup TnUGrl ascenso takes place by the co-operation of the allotters LEOI, y

r2.11101 and L01.

It will be seen from the'foregoing explanations that a relay set ER, for example the set ER4 included in the vsets vmarked ERI-1h, has access to each subscribers line in each subgroup of any line group. While each first intermediate line LZLe cannot be connected with each group intermediate line 2.ZLe and while each of the latter cannot vbe connected with each intermediate line 3.ZLe, a connection with a'selected subscriber can always 'be established so long as such subscriber can reach an idle subscriber intermediate line ZL! which has access to an idle group intermediate line 2 ZLe.

The incoming traic in each line group is thus taken care of First: VOver 50 first intermediate lines 1.ZLe which have access in common to all line groups;

Second: Over 20 group intermediate lines 2.ZLe; and y Third: Over 50 intermediate lines 3.ZLe, ten of which are provided exclusively for each subgroup of lines.

The numbcrtof first intermediate lines .ZLe must be equal to the number of relay sets, so that each subscribers line, so longV as it can reach a group coupler of its group, has access to a relay set from which proceeds the impulse for the completion of the call. If the number of iirst intermediate lines 1.ZLe were smaller than the number of relay sets ER, it might happen that a selected line is` accessible to the associated group coupler GK, over the intermediate coupler ZK, ibut that the relay set ER (from which the marker impulse proceeds) is not available due to busy condition of all iirst inter- `mediate lines 1.ZI.e which are available to it.

In order to take care of the traffic load assumed in the example shown, l5 or 16 intermediate lines 2.ZLe, available to a subgroup TnUGr, 5 would have access would be suicient for each line group T nGr of 250 subscribers lines, provided that traflic from neighboring groups would not have to be considered. It would then be possible, as clearly indicated in Fig. 2, to save in 'each' group coupler EGK 40-50 coupling relays and in each intermediate coupler EZK 4-5 coupling relays. However, of the third intermediate lines 3.ZLe, available to a subgroup TlzUGr, 5 would have access only to one group intermediate line 2 ZLe. Such a ygrouping is in view of busy conditions unsuitable. The intermediate lines 3.ZLe which may be coupled only with one group intermediate lines 2 ZLe will often be busy at times when the group intermediate lines available to them are busy by connections with subscribers lines of other subgroups. These intermediate lines 3 ZLe therefore would be insuiiiciently utilized. The consequence would be that the number of incompleted calls *'due to busy conditions of connecting paths would be excessive. If it were desired to reduce the number of incompleted `connections while using -16 group inter- `ber .of .coupling relays for subgroups each with A5.,() lines would then increase in each line coupler by 100 relays. If only the number of coupling relays in each line group of 25() lines is considered, it will be seen, that the saving of 5() coupling relays in the group coupler GK and 5 5=25 coupling relays in the intermediate coupler ZK is to be compared with an additional expenditure of 5 l00=500 coupling relays in the line couplers and at least 5 2=10 coupling relays in the intermediate couplers ZK. It is therefore more economical, as proposed by the invention, to provide more group intermediate lines than would be required by the prevailing traffic requirements.

Description of Fig. 2

This iigure shows 'the various connecting paths in the line group TnGrl. Of the relay sets there is shown only one (ER4) which is represented by a rectangle. The rligure also shows the precouplers VKl and VKS which are respectively associated with the relay sets ERI-10 and ERM-50 indicated in Fig. l. Of the precouplers VKZ and VK4 there are shown only a few coupling points.

The relay set ER4 has access to the intermediate lines 1 ZLe1-10 (the group 1.ZLeI) over the precoupler VKL Each of these intermediate lines can for connections with subscribers of the group TnGrl be coupled with 4 of the group Z.ZLeI of group intermediate lines over the group coupler GKl. The group 2 ZLI contains the intermediate lines 2.ZLe1-20. For example, the intermediate lines 1.ZLe1 and 1.ZLe6 can be connected together with the group intermediate lines 2.ZLe1, 2, lliand 12, and the intermediate lines 1.ZLe2 and 7 can be interconnected with the group intermediate lines 2.ZLe3, 4, 13, 14. If a connection is to be made to the subscribers line Tn 21124 (see dotted line at left of Fig. 2) which 'belongs to the subgroup TnUGrl, it will extend over the intermediate coupler ZKl. In this coupler can be reached the group intermediate lines 2 ZLe1 and 2, from theintermediate line 3.ZLe1=ZLt10 and the group intermediate lines 2.ZLe11 and 12 from the intermediate line 3.ZLe6=ZLt5. The path to be used for the connection is determined by relays in the allotters L01, 1 EO1 and 2.EO1 which prepare and complete the respective busying and testing circuits.

Of the two intermediate lines 1 ZLe1 and 6 which may be coupled with the same group intermediate lines, one, for example, 1.ZLe1 will always be preferentially seized. Only if this line is busy will the other intermediate line 1 ZLe6 be made available. This sequence of seizure is controlled by busying relays which are arranged ahead of the branching of the intermediate lines to the different allotters LEO.

Once a calling subscriber is connected with the relay set ER4, over the group selection stage GWSt, there will be connected to it (ER4)' over the coupler EK an idle register ZE. After receipt of the series of dial pulses by the digit relays in ZE, the line of the called subscriber Tn 21124 is marked in the marker EF which is connected to the main group. If the line is idle, it will be marked for coupling and a call marking will be produced in the allotter L01. The marker EF determines at the same vtime those branches of the intermediate lines 1.ZLe over passes the coupler GKl, those group intermediate lines which happen to be idle but cannotbe used .due to'busy then be required for each subgroup of lines. AThe numcondition of lthe first intermediate lines LZLe which are accessible thereto. The third intermediate lines `3.ZLe- -ZL1 which have access to the non-available idle group intermediate lines are now disconnected by the .allotter 2.1301 along conductors` which `by-pass the intermediate coupler ZKl. Accordingly, a subscribers intermediate line ZLt and its branch 3.ZLe for incoming calls, having access to group intermediate lines 2.ZLe which in turn have no access to an idle intermediate line 1.ZLe, will not be made available. If the intermediate lines 1 ZLe1 and 6 are busy,`the subscribers intermediate lines `ZL110=3.ZLe1 and ZL15=3.ZLe6 must not bemade available since these two intermediate lines are over the group intermediate lines 2.ZL1, 2, 11 and 12 connectable only with the busy intermediate lines 1.ZLe1 and 6.

It may be mentioned in concluding the description of Fig. 2 that the talking path is indicated by prominent lines. It extends to the subscribers line 21124 from the relay set ER4 over the pre-coupler VKl, the intermediate line 1.ZLe6, the group intermediate line 2.ZLe1, the intermediate line 3.ZLe1 and the intermediate line ZLt10i The manner in which the various operations are performed will now be described with reference to Figs. 3 to 5.

Description of F gs. 3-5

Upon seizure of relay set ER4 (Fig. 3, part 1) by a calling subscriber, there will be energized, in the last coupler of the group selection stage NK the coupling relay Kg which closes over its Contact 1kg the holding circuit by way of the seizure'relay Ce4. An idle register ZE will be connected over the coupler EK.

The relay Ce4 closes a circuit for the relay T, namely,- circuit `1. From ground, contacts 306ce4, 30711, 30811,309g,1re-

lay T, resistor 310, resistor 311, to battery.

2. From ground, contacts306cre4, 30711, 308m 313t, winding I of relay Kz, winding I of relay Cz, contact 3140t to battery. i

At contact 315cz there will be closed a circuit 3. From ground, contacts 306ce4, 307p, 30811, relay G,

relay N, contact 316kz, winding II of relay Kz, resstor 3, winding IIof relay Cz, contact 315cz, relay O1, to battery.

Only the relays G and O1 energize in this circuit. The relays Kz and Cz are maintained energized. The relay N does not receive sufficient current to operate. The re- ,lay O1 opens its contact 31401 and closes its contact 31701 thus preparing for the seizure of the next idle register (not shown). Such seizure takesplace upon `Closure ot' a circuit, in the other relay set, corresponding to the circuit 2. The circuit l is interrupted at contact 309g and relay T deenergizes. The next idle register can now be seized by another relay set. Contact 30811 is shunted at contact 387g. Uponclosure of contact 327kz a circuit will be closed for relay I, namely, circuit 4. From ground, contacts` 328114, 32911 of a control relay (not shown), contacts 327kz, 330g, winding of relay I to battery. 1

Relay I upon energizing opens its contacts 3311', 3331', 335i and closes` its contacts 332i, 3341' and 336i.` The first received impulses control the hundreds relays `H1-H5. The closure of contact 332i has no etect so farA as the relay H1 -is concerned because the ground potential requiredfor the successive energization and deenergization of vthe relays Hl-HS has not yet been connected tothe conductor 326 over the contact chain 321cz, 322t1, 323,111, 324S1, 32511. 1 1 l The hundreds relays III-H5, the tens relays Zl-ZS andthe units relays El-ES are affected similarly by the transmitted current impulses; Accordingly, only the control of the hundreds relays by an impulse series comprising ten (10) impulses will be considered in the following discussion. The circuit conditon of the relays, upon receipt of each impulse, will determinethe energization of the tens and units relays upon receipt of the same number of impulses. 1

The hundreds relays Hl-HS are affected as follows: The relay A4 which is connected tothe upper line conductor responds to each impulse which is transmitted from a preceding repeater (not shown) disposed in the connection. Relay A4 energizes in response to the first impulse. The control relay V is energized in the circuit 5. From ground, contacts 301ce4, 302p, 303114, windings I and II of relay V.

The winding I is shunted at contact 304V, thus making the relay slowto-re1ease, and holding it during the re-y ceipt of an impulse series. Relay V1 inthe register ZE is now energized in the circuit 6. From battery, resistor 318, contacts 305V, 31911, 18kz,

320g, winding of V1, to ground.

7. From ground on conductor 326, contacts 332i, 338h2,

winding of relay H1 to battery.

. Contact 339111 is opened upon energization of relay H1 and contact 337111 is closed. The winding I of the relay H2 is now switched in, but such winding is for the time being shunted overrthe contacts 337111 and 332i.

The relay H1 is energized upon receipt of the rst impulse denoting the selection of the digit 1" and provided that no further impulse is received. The contact 331i is closed upon receipt of the second `digit and relay H2 energizes 1n a circuit 8. From ground at the conductor 326,. contact 337111, wrndlng I of relay H2, 3311' inl parallel with 338112, winding of relay H1 to battery.

In this circuit 8, the winding II of the relay H2 is connected parallel to relay H1 by the opening of the -contact 338112 and closing of contact 352112.

Upon conclusion of the second impulse, the relay H1 is disconnected at contact 331i and deenergizes. `The relay H3 energizes in the circuit 9. From ground on conductor 326, contacts 340111, 341112, winding I of relay H3, contact 342114, resistor 343 to battery.

The relay H3 actuates its p contacts, opening contact 344h3 and completes at contact 345h3 a holding circuit over its winding II and resistor 346. Upon opening of the contact 337111, in the above traced circuit 8 there will result a holding circuit for therelay H2, namely,

10. From ground on conductor 326, contacts 332i, 352h2,

winding II of relay H2 to battery. p p p Relays H2 and H3 are now energized. i s

f 7 "'.Contact'332i isopened responsive to receipt ofthe Vthirdr impulse, and the holding circuit 10 extending oyer the Windingk II .of the relay H2 is Vthereby interrupted. The relay H2 deenergizes and opens the circuit 9. The relay H3 remains energized over its winding 1I. ,'Upon conclusion of the third impulse and consequent closure of contact 332i, relay H1 will again energize in the Ycircuit,'/'. y After receipt of the third impulse', relays H1 and H3 'willbe energized. p

Relay 'H2 is energized over the circuit 8 upon receipt of the fourth impulse. Relay H1 remains actuated over its holding circuit. The relay H4 now energizes in the circuit 11.` From ground on conductor 326, contacts 347111, 348112, winding I of relay H4, contact 345113, resistor 346 to battery.

Upon actuating, relay H4 closes at its contact 349114 a holding circuit `over its winding II and resistor 343. Relay H1 deenergizes upon conclusion of the fourth impulse because both contacts 331i and 338112 are openV at that instant.

At `the conclusion of the fourth impulse the relays H2, H3 and H4 will therefore be actuated.

Contact 331i opens upon receipt of the fth impulse and relay H2 accordingly deenergizes because its holding circuit l is interrupted. Upon conclusion of this impulse, relay H1 energizes over the circuit The relay H3 is now caused to deenergize by current flow over its opposing winding III, in the circuit 12. From yground on conductor 326, contacts 347111,

V350112, 351114, opposing winding VIII of relay H3, con- ;tacts 345113, resistor 346 to battery.

After Yreceipt of the fifth impulse, relays H1 and H4 are accordingly energized Relay H2 -is actuated in the circuit 8, upon receipt ofthe sixth impulse. Upon conclusion of this impulse and consequent opening of the contact 331i, the relay H1 will deenergize. The relay H5 is now actuated in the circuit 13. From ground on conductor 326, contacts 339111, 353114, Winding I or relay H5, contact 344113,resistor 346 to battery.

Relay H5 closes its contact 354115 thereby completing 'a holding circuit over its winding II. The relay remains actuated during the receipt of the further impulses.

The 'relays H2,'H4, and H5 are accordingly energized upon receipt of the seventh dial impulse when contact 332i is opened, thereby opening the holding circuit "10 for the relay H2 and causing restoration of such relay. Relay H4` is now deenergized by current flow over its opposing winding III in the circuit 14. From ground on conductor 326, contacts 340111,

355112, 356113, opposing Winding III of relay H4, contact 349114, resistor 343 to battery.

At the conclusion of the seventh impulse and consequent closure of contact 3321', the relay H1 energizes in the circuit 7'while relay H5 is still actuated.

Relay 1 deenergizes uponv receipt of the next following (8th) impulse, completing over contact 3311' the energizing circuit 8 for relay H2 over its winding I. Relay H restores upon actuation of relay I and the relay H3 energizes over the circuit 9. Y After receipt of the 8th impulse, relays H2, H3 and H5 will accordingly be energized.

Upon kreceipt of the 9th impulse, relay H2 restores again and relay H1 is energized over the circuit 7 at the conclusion of this impulse.

Relays H1, H3 and H5 are now energized.

Upon receipt of the 10th impulse, relay H2 will be actuated over the circuit 8. .Relay H4 thereafter eneraereas gizes over the circuit 1'1 and continues to hold over its YWinding II. Relay H1 restores upon actuation of the relay J and consequent opening of contact 3311'. Relays H2, H3, H4 and H5 will be in actuated position at the conclusion of the 10th impulse, that is, at the conclusion of the impulse series denoting the digit 0. The following .table indicates the relays H1 H5 that are. energized incident to the impulses 1-O. vThe relays Zl-ZS and El-ES are controlled in identical manner and these relays have therefore been included in the table in parentheses.

Relays I l R d mpu ses eceive H1 H2 H3 H4 H5 (Z1) (Z2) (Z3) (Z4) (Z5) (E1) (E2) (E3) (E4) (E5) Further impulses are not received and contact 303114 15. From ground, contacts 360cz, 399111 or 361112, windof relay R, conductor 326 and thence over the holding windings of the relays H that had been energized in accordance with the number of the received impulses, to battery.

Only one Vhundreds impulse had been received in the assumed case of a connection to the line 21124, and the circuit 15 therefore extends over the Winding of relay H1 (332i, 338112, H1).

Contact 3251' is opened responsive to the actuation of the relayR and contact 3621' is coincidently closed. The connection of ground or plus potential to the conductor 364, for affecting the tens relays Z1-Z5 upon receipt of the tens impulse series, is prepared by the closure of contact 3621'.

Only one impulse has been received, and at the end of such impulse, only relay H is energized. Accordingly, as shown in Fig. 3, part 2, the hundreds conductor H111 is now marked over the contacts 363114, 4111, 365115, 366113. A circuit for the relay H11 in the marker EF, which will be closed later, is now prepared. Relay H11 is the rst hundreds relay in the 21st thousands group.

In accordance with the tens digit 2 of the line to be selected, the impulse series which is to affect the tens relays Z1-Z5 of the register, comprises two impulses. Upon receipt of these impulses, the relays Z2 and Z3 will be energized. The relay S1 is actuated in the circuit 16. From ground, contacts 36702:, 368z2, relay S1, conductor 364 and thence over the windings of the energized relays Z2 and Z3 to battery.

9 The tens conductor za2 is now marked over the contacts z3, 6z2, 373z4 and 37425 of the circuit formed by the contacts of the relays ZI-ZS, because only the relays Z2 and Z3 are in actuated position. Over this tens conductor za2 will be subsequently energized, in the marker, the tens relay Z12 of the first hundreds of the 17. From ground, contacts 380cz, 381e2, relay T1, conductor 370, and thence over the windings of the energized relays E2, E3, E4 to battery.

The energization of the relay T1 is a criterion for the receipt, in the register, of the dial digit series required for completing a desired connection. Relay T1 opens its contact 3S1t1 and closes its contact 38211. The relay Pzl now energizes, provided no signal is present at this instant, from another register, by the closure of an associated contact corresponding to the contact 382t1 to signify the completion of a connection which would cause the test relay of such other register, for example, relay Pz2 of the register ZE2, to operate thereby opening the contact 383pz2. The relay Pzl energizes in the circuit 18. From ground, resistor 388, contacts 385sp, 386pzn, 383pz2, 387pz1, 38211, relay Pzl, relay Sp to battery.

Relay Sp energizes upon shunting of the resistor 388 at contact 389 pzl and opens its contact 385sp. In the relay set ER4, the relay N will be actuated becauseA the resistor 3 disposed in the circuit,3 will be shunted at Contact 11pz1. Contact 319n is openedresponsive` to the actuation of relay N and contact 12u is closed. The relay H11 in the marker EF will now beconnected over the circuit formed by the contacts of the hundreds relays Hl-HS (Fig. 3, part 2) such circuit being 19. From ground, contact 390cz, relay Q, contacts 13pz1, 363h4, 4h1, 365h5, 366h3, conductor hal, relay H11, resistor 16 to battery.

The energization of the relay H11 serves as a criterion that a connection is to be completed 'in the lst `hundred of the 21st thousand group. The relay H11 closes its contacts and thereby connects all of the ten tens relays Z11, Z12 Z10. Only the tens relays Z11, Z12 and Z13 are shown. The tens digit 2 having been dialed, the tens relay Z12 will energize in the circuit i 20. From ground, `contacts 39202, 14pz1, 5233,A 6272, 373z4, 374z5, conductor m2, contact 17h11, relay Z12, resistor 16 to battery.

The relay Z12 closes its contacts Z12, each of these contacts connecting one units conductor ea with the cor responding subscriber line of the 2nd tens group. The number 21124 having' been dialed, the circuit is now prepared at contact 20212 over which a subscriber line is controlled.

The` relay Q which operates in the circuit19 opens its contact 320g and closes its contact 394:1. There is now closed the testing circuit 2l. From ground, relay F, contacts 12n, 18kg, 394:1, conductor 395, contacts pz1, 7e3, 8e2, 9e4, 10e5, conductor ea4, contact 20z12, conductor m21 124, to

2,2121, Windingl of relay 'Ka1, conductor 23',`relay An1 to battery.` -i i The relays F, Ka1 and Anl` energize. Relay Anl, at

its contact 26an1 disconnects ground from relay R1 which is energized only in calls outgoing from a subscribers line.V No coupling marker signal can now be produced on any of the subscribers lines in the group until interruption of the circuit traced at 2l and consequent de-energization` of relay Anl.` At contacts 27ka1, relay Kal short-circuits its Winding II. The signal marking the coupling is produced by the contact 281ml (of relay Kal) which connects ground to the energizing windings of all the coupling relays such as Kt15, Kt which can switch connections through to the subscribers line 21124. At contact 291ml is prepared the holding circuit which will be closed after switching through the talking path from the relay set ER4 to the subscriber-s line Tn 21124.

The relay Anl initiates the selection of an idle intermediate `subscriber line ZLt. These intermediate lines are in incoming calls taken into use in the sequence 10, 9, 8, etc. instead of in the sequence 1, 2, 3, etc., as in the case of outgoing calls. The circuit of the relay Qe which initiates the coupling of the intermediate subscriber line to be used with the selected subscribers line extends over the contact 30ml. Before the coupling can be initiated, it is necessary to ascertain whether the idle intermediate subscriber line ZLt10 and its branch 3.ZLe1 have access to the relay set E114 (connected with the calling line), over an idle intermediate group line 2.ZLe and an idle rst intermediate line 1.ZLe. The test for ascertaining this condition is initiated by the closure of contact 31an1.

The test relay F in the relay set ER4 has closed the contact 32]c (left lower end of Fig. 4), thereby connecting battery to the conductor 33 leading to the Winding of the coupling initiation relay Qr4 and ralso to the relays SE11-SE21 etc. in the allotters 1.130144.` `The relay SE1 in the allotter 1.EO1, Which is associated with the group in which the connection is to be made, energizes and an idle intermediate subscriber line ZLt (in the line coupler of the subgroup of the selected subscribers line) which cannot be connected with the marked relay set due to lockout from second or first intermediate lines (2.ZLe, LZLe), consequently cannot `be made available for the call. This is done by marking the `locked out first intermediate line 1.ZLe of the first stage.` Since a connection is to be made in the subscriber group TnGrl (numbers 21l00-2l350), .the` circuit for the busy or lockout relay SE11 in the allotter 1.EO1 is closed. Each group of subscribers lines comprises 250 lines.` The first line group is marked when one of the tens relays (Zlib-235) having the contacts l0-235 has energized. In the present case, the tens relay Z12 is energized, the corresponding contact 34z12 (right lower end of Fig.` 3, part 2) is operated and a circuit is completed for `the relay SE11 as follows:

22. `From ground, contact 34z12., conductor 35, winding of relay SE11, coupling-initiation relay Qr4, conductor 33, closed contact 32j to battery.

The relay Qr4 closes its contacts qr4, thereby connecting `the winding l of the test relay P (Fig. 3, part l) with all coupling relays lil-K10 of the relay set E114 in the pre-coupler VK'I. lust Which of the coupling relays will energize will depend ou the rst, second and third intermediate lines 1.ZLe, 2.ZLe and 3.ZL3 (ZLt) which are to be used for the'call.

As is apparent from Fig. 2, the intermediate line 1.ZLe1 as Well as the intermediate line 1.ZLe6 in the linal group coupler GKI have access to the intermediate group lines 2.ZLe1,"2, `11 and 12, and also (see Fig. 1)

Fig. `5, contact 21ar1, relay Kal winding ILVcontact 75 over the group couplersGKZ-t access Vto the correspondi- 11 ing intermediate group lines 2.ZLe21, 22, 31, 32, 41, 42, 51, 52, 61, 62 and 71, 72 which are associated-with the subscribers groups TnGr2-44.

The intermediate group lines 2 ZLe1 and 2 may be coupled with the intermediate lines 3.ZLe1 (in the coupler 2K1); 3 ZLellll (in the coupler ZKZ.) etc., while the intermediate group lines 2 ZLe11 and 12 may be connected with t-he intermediate lines 3.ZLe6 (in the coupler ZKl); 3.ZLe16 (in the coupler ZKZ) etc. It follows therefore that the idle intermediate subscriber line ZLt10 (=3.ZLe1) can be made available for a connection only if one of the intermediate group lines 2.ZLe1 and 2 and one of the intermediate lines 1.ZLe1 or 6 of the tirst group 1.ZLe1 (Fig. l) are idle. The intermediate subscriber line ZLtS (:3.ZLe6) may however be also coupled with the first intermediate lines 1.ZLe1 and 6.

Only some of the many possible busy or lockout conditions will now be explained. l

It shall be first assumed that the intermediate subscriber lines ZLz10=3-ZLe1 and ZLt5=3.ZLe6 are idle, and that the intermediate group lines 2.ZLe1 and 6 are busy due to connections which extend over the couplers ZK2-5 of the subgroups TnUGrZ-S. The relays C51 and C52 which are disposed in the allotter 2.E01 (Fig. 5), with their wind- 4ings I in the holding conductor are in such a case energized. The contacts 36c51, 377c52 are closed so that the krelay C010 in the allotter L01 will energize upon closure of the contact 316ml in a circuit 23. From battery, contacts 31ml, 381'1, winding II of relay C010, contacts 36u51, 37c52 to ground.

Relay C010 opens its contact 390010. The couplinginitiation relay Qell cannot energize. The chain serving for making available an idle intermediate line switches further. ln the corresponding circuits there will be energized the busy or lockout relays of those intermediate subscriber lines which (like the intermediate line ZLt10) have no access to an idle intermediate group line. For example, if the intermediate group line 2.ZLe11 and 2.ZLe12 are busy, the relays C511 and C512 will be op erated. The contacts 41c511 and 420512 are consequently closed and the lockout relay C of the intermediate subscriber line ZL15=3-ZLe6 will operate to disconnect the couplingdnitiation relay Qe5 at its contacts 43co5 and to switch the chain through at contact 44co5.

Ground is also connected to the lockout conductors, leading to the other allotters LO25, by contacts of the relays C51, C52, C511, C512. Relays corresponding to the relays C010 and C05 in these allotters do not energize if the associated intermediate lines are idle, because the call receiving relays An are not energized in these allotters.

If the intermediate group lines 2.2Le1 and 2 are idle, there is still no assurance that the talking path can be completed over the intermediate subscriber line ZLI because the first intermediate lines 1.ZLe1 and 6 of the first stage (which are accessible from the final selection relay set ER4 and with which the intermediate group line ZZLei and 2 may be coupled) might be busy by connections extending to subscribers of other groups.

Assuming the intermediate group lines 2.ZLe1 and 2 to be idle, there will be no current flowing through the windings I of the lockout relays C51, C52 in the allotters 2.1301. Second windings of these relays are however connected to the lockout conductor 401. A potential is connected in the allotter 1.1501 to this lockout conductor and also to the lockout conductor 406 which belongs to the intermediate group lines 2.ZLe11-12 (also accessible to the intermediate lines 1.ZLe1 and 6), because the lockout relay SE11 is energized in the circuit 22 traced before, and because the lockout relays C1 and C6 are connested in the holding conductors of the busy intermediate lines 1.Zl,e1 and 6. The relays C51 and C52 therefore energize responsive to the energization of the lockoutinitiation relay SE11 in the circuit 12 24. From ground, contacts c6, 46c1, 47se11, conductor 401, relay C52 (winding Il), relay C51 (winding II) 'to battery.

Another circuit is completed for the relays C512 and C511 25. From ground, contacts 4806, 4961, se11, conductor 406, winding Il of relay C512, winding II of relay C511 to battery.

Circuits over windings II of relays in the allotters 21202-4 corresponding to the relays C51, C52, C511 and C512 are not completed because the lockoutinitiation relays SE124 in the allotters 1.12024 are not energized. For example, the lockout-initiation relay SE12 in the allotter 1 E02 is energized only after selection of a subscribers line in the group TnGrZ.

As explained before, the lockout relays in the allotters LOZ-5 of the other subscribers groups TnUGrZ-S, corresponding to the relays C010 and CO5 in the allotter L01 are not operated.

If the intermediate lines 1.ZLe1 and 6 are busy and if a connection is to be set up from a group having a relay set which is not associated with the pre-coupler VKL for example, from the relay set ER24, the closed contacts 45c6, 46d and ic, 49d will not atect the lockout relays C51, C52 and C511, C512, because the lockout-initiation relay SE11 is not energized in such a case, but the relay SE31 associated with the third group of relay sets `is energized. The lockout relays C51 and CS2 (windingrli) can energize in a circuit over the conductor 401 and contact 51se31 only if the relays C26 and C21 of the intermediate lines 1.ZLe21 and 26 are energized and their con tacts 52c21 and 53c26 closed. Therelays C511 and C512 (windings Il) will in such a case also energize over corresponding contacts and the conductor 406.

No matter from which final selection relay set the signal for setting up a call is given, the making available of idle second and third intermediate trunks is always inhibited if the involved relay set cannot be reached from such lines due to lockout of the lirst intermediate lines. If both rst intermediate lines 1.ZLe1 and 6 and also both intermediate group lines 2.ZLe1 and 2 are idle, the connection will be set up over the intermediate lines 1.ZLe1 and 2.ZLe1 because the coupling conductor is in such lines switched through over the reStingcOntacts of the associated lockout relays C1 and C51.

If the intermediate line 1 ZLe1 is busy, the lockout relay C1 will be energized. The contact'54c1 .ofl this relay is opened. A coupling circuit cannot be established overthe corresponding conductor, but can be established over the coupling conductor of the intermediate line 1.`ZLe6 which has been switched through at contact intermediate line pairs (1.ZLe1-6) are busy or lockedV out, so'as to prevent making available an idle third inter mediate line pair which can be coupled only with the locked out pair of intermediate lines LZLe.

' The sequence in which the intermediate lines of yu pair (1.ZLe1, 6-2.ZLe1, 2 or 11, 12) are taken into use is determined by the busy or lockout relay (C1, C51, C511) of the line of the pair which is to be used first. When the signal for the setting up of a connection to the subscriber 21124 becomes eiective, that is, when the relays Anl vand SE111 in the allotter L01 and in the 13 allotter 1.1301, respectively, energizethus indicating that the intermediate lines ZLt10=3.ZLe1, 1.ZLe6 and 2;ZLe1 are idle. `The intermediate lines 1.ZLe1 and 2.ZLe2` are busy. The contacts 56c51 in the allotter` 2.E01, Fig. 5,

and 5501 in the allotter 1.EOV1, Fig. 4, are closed.

Since the relay C010 in the previously traced circuit 23 is not energized, the coupling-initiation. relay Qe10 for incoming calls, and also relay Qh, will energize in the allotter L01 in a circuit. Y

26. From ground contacts 300ml, 58qh, 59r1, 39co10, windingof relay Qe10, winding of relay Qh to battery.

A holding circuit will now be completed for both of these relays 27. From ground, contacts 60ml, 62qe10, winding `of relay Qe10, winding of relay Qh to battery.

The above traced circuit 26 is opened at contact 59qh and relay C010 energizes` in a circuit 28. From ground, contact 63qe10, winding II of relay C010, contacts 381'1, 31an1 to battery. n

The relay Q10, upon energizing places at its contactV 66q10 a potential on that coupling relay of the `subscribers line 21124 which can connect such line with the intermediate subscriber line ZLt10 having the branch 3.ZLe1 for incoming calls which is to be used for the connection to be set up. In the assumed case, the subscriber coupling relay Krl10 will energize in a circuit 30. From ground,` contact 28ka1, winding I of relay K`t110, conductor 67, contact 66q10 to battery.

The coupling of the subscribers line Tn 21124 with the intermediate line ZLt10 is effected by contacts 68kz11, 69kt110 and 70kt110.

The branch 3.ZLe1 of the line ZLt10 which is to be used for incoming calls is coincidently coupled withthe intermediate line 1.ZLe6 in a circuit 31. From ground (Fig. contact 65qe10, `winding I of 4coupling relay Kzll, contact 56c51, conductor 71 to Fig. 4, winding I of, coupling relay Kg61, contact 55c1, winding I of coupling relay K6, ,contact 72qr4,

' conductor 73 to Fig. 3 part 1, winding I of relay P to battery. r f

The following coupling operations are effected:

The intermediate lines 3.ZLe1/2.ZLe1 are coupled at contacts '74-76kz11; the intermediate lines 2.ZLe1/ 1.ZLe6 are coupled at contacts 77-79kg61; and the interl mediaterline 1.ZLe6 is coupled with` the final selection relay set ER44 at contacts 80-82k6.

There is now established a holding circuit 32. From ground at Fig. 5, contact 29ka1, winding `II of theline relay ARl, winding I of the cut-off relay TR1, contact kt11, Winding II of the coupling relay Kill, conductor 83, winding III ofthe busy or lockout relay C010, conductor 84, contact 76kz11, winding II of the coupling relay Kz11, winding I of the lockout relay C51, conductor to Fig. 4, winding II of the coupling relay Kg61, contact 79kg61, lockout relay C6, `contact 82k6, winding II of the coupling relay K6, conductor 86 to Fig. 3 part l, winding II of relay P, `contacts 87p, 88x, 891,` resistor 90 to battery.

-The cut-olf relay TR1 disconnects the call bridge `and therewith the winding I of the line relay ARl at its con- Aes '14 previously traced ci1'cuitn"2l.` `The relays An1Ka1 (Fig.,5) and F (lf"ig.,3)` deenergze. The contact 29ka1 Opens thereby removing the `shunt around the ,meter Zal of the called line; and thus connecting the meter in the circuit 32 noted above. The previously traced circuits 27 28 and 29 are opened by the deenergization of relay A111 in the allotter L01. The previously traced circuit 3 in the relay set is interrupted (at contact 30fp)` as a consequence of the energization of the relay P in the previously traced circuit 31. The path for the setting up of the call is now freed. The shunt of the relay Sin the relay set ER4 (Fig. 3 part l) is removed at contact 89j responsive to the deenergization of relay F. Relay S energizes and effects switching operations which have no particular bearing on the invention, such as switching through the line conductors to the selected subscriber. 1

The connection between the relay set ER4 andthe called subscriber 21124 is now completed. The connection may be traced from the switching device ER4 (Fig. 3, part l) which had been assumed to have been seized .by` a group selection device GWSt (Fig. 2), conductors at the top` of Fig. 3, part l, over to Fig. 4,`and from there, following the prominently drawn. line conductors, over closed contacts 80k6-81k6, 77kg61`-78kg61, to Fig.V 5,` thence over contacts 74kz2-75k11, 68kt1- 69kt10, `the line conductors terminating in the station of the called line Tn 211 24 as shown. The functions of the line and cutoi relays ARI and TR1 of the called line have been explained before.

The lockout-initiating relays SE in the allotters 1.E0 are energized only for thebrief interval required for completing a call. The cturent consumption required f orlthe busying or lockout of the intermediate lines which, although, idle, cannot be used :for Va connection to be set up due to lockout of intermediate lines of other stages, therefore amounts only to a lfraction of what would be necessary without these lockout-initiating relays. These relays also simplify the circuits needed for carrying out the lockout. @For example, when a signal is received in the allotter L01 of the group TnGrl for the setting up of an incomingcall, there must be marked in such allotter just which of the idlefthird intermediate lines (3.ZLe/ZLt) are to be disconnected if. the rst intermediate lines (LZLe), which are available to these idle lines, are'busy or on lockout dueto connections existing in other line groups.

Inasmuch as the conditions in all parts of rst inter.- mediate lines are identical, the following explanations will refer only to the intermediate lines 1.ZLe1 and 6 which are accessible to the relay sets ER4.

If the lockout-initiation relays SE114 were not provided, `all line groups in the allotters 2.E 014 would have to be marked always at times when the two intermediate lines 1.ZLe1 and 6 are on lockout. With these rst intermediate lines may be coupled in each line group two pairs, that is, eight'pairs of intermediate group lines 2.ZLe. These are:

(a) `In coupler GK1 intermediate `lines 2.ZLe1, 2; 11, 12. (b) In coupler `GKZ intermediate lines 2.ZLe21, 22;

31, 32. `(c) In couplerrGK3 intermediate lines 2.ZLe41, 42;

" 51,52. (d) In `coupler GK4 intermediate lines 2.ZLe61, 62;

Only two of these sixteen intermediate lines can be coupled together with the intermediate lines 1.ZLe1 and 6. In these lines, thelockout relays disposed in the lockout conductors, such as C51 (winding I)` and C52 :(winding I) are energized by current flowing in the holding circuit. However, the other fourteen intermediate group lines must -also be marked as busy or locked out tactsltrlfand 92tr11. `At `its contact 22tr1 it opens the ,15 inasmuch as they maybe idle but not useable. It must 'i5 bef considered that intermediate subscriber lines ZLt :third intermediate lines, .3.ZLe, must be made available which have access to these intermediate group lines. Lockout relays of these intermediate group lines therefore must always be operated so long as theintermediate lines 1.ZLe1 and 6 are on lockout. Y

Considering the 80 intermediate group lines of each principalgroup there will result a very noticeable current consumption. The current consumption will not be reduced lin the case of :a negative lockout, that is, a lockout in which the lockout relays are energized when lines are idle and at rest when the lines are busy. The current consumption will be indeed somewhat higher since the time during which more than half of the intermediate group lines are used is shorter than the time during which more than half of the intermediate group trunks are idle. The llockout relays C51 C52, C511 and C512 in the allotter 2.1301 and the corresponding lockout relays in the allotters 2 EO2-4 therefore must always be energized incident to lockout of the intermediate lines 1.ZLe1 and 6, in spite of the fact that only two of these trunks 4belong to the intermediate group lines which are involved in calls extending over the intermediate lines 1.ZLe1 and 6. l

The identical expenditure would Ibe required in connection with the lockout relays of those intermediate group lines of all subscribers groups which may be coupled with other busy intermediate line pairs, for example, 1.ZLe3 and 8, 4 and 9, etc. The use of the lockout-initiating relays SE makes it possible to limit the energization of lockout relays of idle but not useable group lines to the short intervals in which the connection of idle subscribers lines occurs in the setting up of calls. The lockout relays are also effectively connected only inone of the allotters 2 EO. Since there is only one marker provided, only one selected subscribers line of all the lines in each principal group can be connected .at any instance and accordingly, one lockout-initiating relay can be coincidently energized.

As will be apparent from Fig. 2, the rst intermediate lines 1.ZLe11, 16, 21, 26, 31, 36, 41, 46 which are not "accessible to the calling relay set ER4 have access to the same intermediate group lines, 2.ZLe1, 2, 11, 12. Since an energized lockout-initiating relaySEl1 indicates clearly from which group of the relay sets the signal comes, no marking is required to indicate the operating conditions with respect to the above noted rst intermediate lines which cannot be reached from the signalling Vrelay set ER4. However, if the lockout relays were not provided, it would always be necessary to consider the `operating conditions of these 'rst intermediate lines, thus resulting in complicated circuits.

The circuit for the lockout-initiating` relay SE11 is completed responsive to closure of one of the contacts of the tens relays Zll-ZSS, which are disposed in parallel. The parallel circuit for the 25 contacts may ,be avoided (in groups comprising 250 lines) ,by employing-as shown in Fig. 3a, an auxiliary relay HRl for each group of 2,5 tens relays which mark a group 015,250 subscribers lines.

The relay HRl energizes in series with the tens relay 212. See previously traced -circuit 20.l At its contact hr1, it connects ground to the conductor 35 (Fig. 3a) thereby closing the circuit for the lockout-initiatingrelay SE11.

The lockout-initiating relays SE11, etc. need not be switched in from the marker EF. The switching in may be carried out from the allotters LO as indicated in Figs. 4 and 5 in dotted lines. The Iconductor 35 and the contacts of the tens relays in the marker lyingparallel thereto may in such a case be omitted.

The relay R1 which marks .the outgoing direction of a call to be set up is not energized when the call receiving or start relay A111 energizes responsive to a signal signifying an incoming call. in the allotter LEOI 'thereupon energizes in a circuit The lockout-initiating relay lSE11 `16 33. Frombattery (Fig. 3., partZ), contact 3232 conduce tor 33 (Fig. 4), coupling initiating relay Qr4, lockout.- initiating relay SE11, conductor 97 (lower right of Fig. 5), contacts 96r1, 95ml to ground.'

The relay SE11 initiates the switching operations already described.

The conductor 97 `also leads to the corresponding anand r-contacts in the allotters LOZ-L05 of the same subscriber group TnGrl. The relay SE11 is energized only when a connection to be set up in the subscriber group TnGr1, just as in the case of its actuation from the marker.

The control of the lockout-initiation relays from the allotters makes it possible to distribute the lines of'a P. B. X group as desired, in several subgroups of a line group as well as in several line groups of a principal group of subscribers lines.

The distribution of the lines of a P. B. X group in different line groups makes it possible to increase their number at any time, without requiring changes in the numbering of the P. B. X group or of other subscribers if free lines are not available in the group to which the P. B. X` group belongs. n

The distribution of the lines of a P. B. X group in Vseveral line groups may however be called for even without increase of the number thereof, if increased tratlic requirements should cause operational diculties. It may happen, for example, that the number of available intermediate `subscriber lines cannot handle'the traic. An increase of the number of intermediate subscriber lines would call for an increase of the number of coupling relays, not only in the line coupler but also in the intermediate couplers. It is possible, by distributing the extension lines of a P. B. X group in several line groups to mix the heavily loaded P. B. X with subscribers lines showing little traic or with subscribers whose peak loads occur at times different from the peak loads of the P. B. X.

A P. B. X group having lines distributed in two line groups will now be described with reference to Fig. 7.

Description of Fig. 7

The talking or line paths are indicated in this figure by single conductors. They comprise, as those shown in Figs. 3-5, four conductors, that is, a coupling conductor, a holding conductor and two line conductors. Further, more, the gure shows in each line group only one pair of intermediate group lines, namely, 2.ZLe1, 2 of the group TnGrl and 2 ZLe41, 42 of group TnGr3, together with the windings of the lockout relays which are disposed in the special lockout conductors. However, `as is apparent from Figs. 1, 2 and 4, the intermediate lines 2.ZLe11, 12, 51, 52 may also be coupled with the intermediate lines 1.ZLe1 and 6 in the two subscribers groups.

The P. B. X group is assumed to have four P.' B. X lines which are distributed in three subgroups belonging to two subscriber groups. The collective number of the P. B. X group is assumed to be 21131. The two'lines 21131 and 21132 belong to the subscriber subgroup TnUGrl and the line 21231 belongs to thesubgroup TnUGrS. These three lines may be Vreached over `the group TnGrl. The fourth line of the P. B. X group has the number 21531. It belongs tothe subgroup TnUGrll 'and therewith to the line group TnGr3.

The P. B. X group is reached over the control conductor or start conductor ma. If the line 21131 is idle, the test circuit 2l extends 34. From the conductor ma, contacts 101tr1, 102ml, winding I of coupling signal relay Kal, conductor 23, Winding of relay Anl to battery.`

`energizes a circuit. i i

38; Frombattery, contact 32j, conductor 33, coupling.,

anregen i. 17 theintermediate group lines 2.ZLe1 and 2. The two relaysenfrgize as already described, when the `two rst intermediate lines 1.ZLe1 and 6 are on lockout.` By closing their contacts 36u51 and 37c52, they switch in the relay C010 thereby preventing that the intermediate subscriber line ZLt==3.ZLe1, although idle, is made available. i i i i The relays C511, C512 (not shown) of the second pair of intermediate group lines which may be coupled with the 4intermediate lines `1.ZLe1 and 6 are also energized in a manner as explained before with reference to Figs. 4 and 5. They prevent making available the intermediate lines ZLt5=3.ZLe6.

If the line2ll31 is busy, the start conductor ma `will be switched to the coupling signal relay Ka2 ofthe second line 21132, by the closure of contact 103tr1. The start circuit then extends over the contacts 103tr1, 104tr2,` 1405ar2, etc. The coupling signal relay Ka2 and the start relay Anl energize and initiate the setting up of the call..`

If the line 21132 is also busy, the start circuit will be switched to the :third line 21231 ofthe P. B. X group. This line does not belong to the subgroup TnUGrl but to the subgroup TnUGr3 which is associated with the line coupler LK3 and the allotter L03. The impulse for` setting up the call reaches the coupling signal relay Ka3 over a circuit ."Ihe relay Ka3 produces the coupling start impulse. The start relay An3 closes the contacts which initiate making available an idle intermediate subscriber line t and also the contacts 111an3 and 112an3. The lockout-initiating relay SE11 is now energized in a circuit 3.6. From battery, contact 32j (lower left of Fig. 7), conductor 33, coupling initiation relay Qr4, lockout` initiation relay SE11, conductors 97, 114, contac `113r3, 112an3 to ground.

i The relaySEll causes upon energizing, the previously described switching operations.

If only the P. B. X line 21531 is idle upon receipt of the call impulse over the conductor ma, the testing will extend in a circuit i 37. From ground on the conductor ma, contacts 103tr1, 106tr2, 115113, 116tr4, 117ar4, winding I of coupling start relay K4, conductor 118, winding of` start relay An11 to battery. i t

The relay Ka4 producesl the `coupling start impulse. The "relay An11 closes among others the contacts 1'20z`n11, 121an11. The lockout-initiation relay SE13 initiation relay Qr4, conductor `124, lockout-initiation relay SE13, conductor 123, contacts 1221'11, 121an11 to ground. i 'i i e i Assuming the intermediate'lins 1'.ZL1` and 6 to be busy and, accordingly,`the lockout relays C1 and C6 to be energized, the lockout relays C41 and C42 ofthe intermediate group lines 2.ZLe41 and 42 will operate in `a circuit 39. From ground (left lower end of Fig. 7 contacts `45c6, 46c1, conductor 125, contact 126se13, lockout relays C42, C41 to battery.

The lockout relay C0110 in the allotter LO11 will now energize in a circuit 40. 'From ground, contacts 127c42, 128041, winding of relay C0110, contacts 129r11, 120an11 to battery.

The lockout relay C0110 prevents taking into use the subscriber intermediate line ZLt10 of the third subscriber group and switches the` and C42 also the lockout relays C51 and `C52 (not shown in Fig. 7) of the intermediate group lines 2.ZLe51 and 52` (also omitted in Fig. -7). They prevent making available a` third intermediate line in the subgroup TnUGrll which has access to the intermediate group lines 2.ZLe51 and 2.ZLe52.

However, if one of the intermediate lines 1.ZLe1 or 6 is idle, the circuits 39 and 40 will not be closed since one or the other of the contacts 45c6 or 46c1 is open. The intermediate subscriber line ZLt10 will lbe made available in the allotter LO11.

. It will be assumed now that the intermediate line 1.ZLe1 is idle. In thiscase, the coupling relays (not shown in Fig. 7),` namely, Kg31l (in the coupler GKS), Kzl1l (in the coupler ZK11) and Kt41o (in the line coupler LK11), will energize. There are to be coupled two line conductors and one holding conductor. VThe coupling is `accordingly effected by the closure of three sets of contacts, each having three contacts, of which only one of each set is shown, namely, contacts 130kt410, 131kz111, 132kg311. The talking path between the relay set ER4 and the subscribers line 21531 extends in a circuit 41. From the relay set ER4, coupling contacts 133k1, rst intermediate line 1.ZLe1, 4coupling contacts 132kg311, intermediate `group line 2.ZLe41, coupling *contacts 131kz111, third intermediate line '3.ZLe1,\ intermediate subscriber line ZLt10, and coupling contacts 130kt4lo to the subscribers line 21531.

The various P. B. X lines of a P. B. X group may also Abedistributed in all groups of a principal group.

Changes may -be made within the scope and spirit of the appended claims.

I claim:

.1. An automatic telephone system off the relay. type comprising a plurality of groups of subscribers lines forming a main `group of lines, each of said groups containing a plurality of subgroups of lines, a plurality of switching devices for said `main group, means for connecting a calling subscribers line to one of said switching devices, a register, a marker, means in said switching device to which a calling subscribers line has been connected `and cooperating with meansin said register and in said marker for selecting a called subscribers line over said register and said marker to mark said line as a called line, a plurality of serially related couplers, a plurality of rst, second and third intermediate lines extending respectively between said couplers, means for extending a talking path from said` switching device to said called line over said serially related couplers and said intermediate lines, one of said serially related couplers being individual to the group of subscribers lines containing the called line, and another one of said serially related couplers being operative to connect: said switching `devicewith any one of said first intermediate lines over said coupler which is individual to the group of lines containing the called line.

2i. A system according to claim l, in which said switching devices are subdivided into a plurality of groups', said last-named coupling means beingtindividualto a group of switching devices, said rst intermediate lines extending between said last named coupling means and said coupler which is individual to the respective line groups, further couplers respectively assigned to subgroups of lines, and intermediate lines extending between each coupler which is individual to a line group and all further couplers of said line group.

3. A system according to claim 2, in which the number of said first intermediate lines is equal to and the number of said intermediate lines assigned to a line @erases devices assigned to said main group.

4. A system according to claim 2, wherein four of' said second intermediate lines are accessible overtwo of said first intermediate lines, means for coupling said third intermediate lines directly with subscribers lines, and coupling means for respectively interconnecting each pair oftwo of said second intermediate lines with one of said third intermediate line.

' 5. A system according to claim 4, wherein predetermined ones of said first intermediate lines which are conne'ctable with corresponding second intermediate lines are preferentially taken into use in extendingv calls, and lockout relay means etective upon taking into use the predetermined first intermediate line for preparing the couplingrcircuit of the other first intermediate line which also has access'to the secondI intermediate linesand for interrupting the coupling circuit of the associated rst intermediate line 'so as to block the seizure of said vfirst intermediate line.

6. A system according to claim 2, wherein predeter` mined ones of said second intermediate lines which are connectable with the Asame third intermediate line are preferentially taken into use in extending calls, and lockout relay means effective upon taking into use a predetermined `secured intermediate line for preparing the coupling circuit" of the other secondintermediate line which also has access to the same third intermediate line and for interrupting the coupling circuit of the associated second intermediate group line` so as to block the seizure of saidV second intermediate group line; t

7. A system according to claim 2, comprising an allotter, al lockout relay in said allotter for each of said third intermediate linesffor thepurpose of preparing idle ones of said third intermediate lines for use, said lockout relayrpreventing upon blocking of an intermediate' line the seizure of an idle second intermediate line which' is connectable thereto.

8. A system according to claim 7, comprising an allotter, and locking relays in said allotter for preparing the seizure of idle third intermediate lines, said locking relays preventing the seizure of an idle second intermediate line if the lirst intermediate lines to which the idle second intermediate line has access is'blocked by' disconnecting this idle third intermediate line which has access to the idle second'intermediate group line which is not to be used.

9. A system according to claim 8, wherein the same lockout relays whichblock busied third intermediate lines also disconnect free third intermediate `lines if the accessible secondintermediate lines are blocked.

10. Asystem according to claim 1, comprising allotters for'said subgroups, said third intermediate lines accessible'to said allotters and connectable with subscribers lines, lockoutrrelays for said third intermediate lines, said secondA intermediate lines intermediate lines,'lockout relays. for said` second in termediate lines, circuit means for operating the last named' lockout relays responsive to seizure of the respective-intermediatelines associated therewith, and a circuit means controlled by the'r operated lockoutrelays for said second intermediate lines for preparing circuits for the energization of the lockout relays for said third intermediate linesonly in an alloter associated with a subgroup in which a signal for extending a call isreceived.

Y 11. A systemA according to claim 2, comprising a plurality of lockout initiating relays assigned to a group of'subscribers lines, a signal associated with a group of accessible to `said third said switching devices for controlling each of said lockout initiating relays, means in said marker for transmitting' said signal after the impulse series corresponding ",tojthel wantedlinehas been received insaid register, meanscomV trolled by the actuation of a lockout initiating relayfor preparing circuits for the lockout relays of the group of second intermediate lines which are accessible to a group of said first intermediate lines, said circuits being closed1 only when said irst intermediate lines are blocked.

l2. A system according to claim 10, comprising a test relay in each of said switching devices, means for causing operation of said test relay when the selected sub scriber line is found idle to close the circuit for the associated lockout initiating relay whichv is assigned to the group of lines comprising the selected line.

lf3. A system according to claim ll, comprising a further relay which is operable jointly with said lockout initiating relay, said further relay initiating the coupling; of said switching device which has been seized bythe calling line with an idle first intermediate line.

14. A system according to claim 10, comprising a lockout-initiating relay for each line'group accessibletto said switching device overV said intermediateV lines, tens relays insaid marker responsive to the tens digits of'called subscribers lines, circuit means for subdividing the contactsk ofsaidtens relays in groups in parallel relationship, theL closure of predetermined ones ofsaid contactsdetermining the line group containing a called subscriber to determine` the energization of the respective Vlockout-.initiating relay.

` 15 A system according to'claim ll, comprising alockout-initiating relayV for each line group accessible to said switching device over said intermediate lines, said marker responsive-to dial'led digits of called lines, and circuit means for energizingsaid lockout initiating relays in'acf cordance with( linesto which calls areto be extended, said' circuit means comprisingl tens relays for marking' they groupsgcontaining selected subscribers lines, anauxi'liary relay common to a group oftensrelays, and circuit means controlled by the energized auxiliary relay for controlling the operation of a lockout-initiating relay for the line group containing the selected line.

16. A systeml according to claim l1, comprising anallotter for each of said subgroups of lines, and relay means' in' said allotters responsive to the extension of a call to the associatedl subgroup'for closing the circuit of the lockout# initiating relay associated with the respective line group.

17. Asystem according to claim 15, comprisingan a1.-v lotterfor each of said line groups, a lockout-initiating relay in said allotter for each group of said 'switching devices, and circuit means for said lockout-initiating relay which by-pass couplers in the linal selection stage. i

18. A system according'to claim 1, comprising 'a P; B1 X group, thelines ofrsaid P. B. X group being disposedin different line groups'each of which is' subdivided injsub# groups, a coupler in each line group, an allotter for each subgroup of lines, and relay meansin said allotters responsive to the extension of calls theretofor switching the setting up of such calls overthe associated coupler..

References. Cited in the tile of this patent UNITED STATES PATENTS 

